Manholes and catch basins for use along roads and streets have been known and used for quite some time. Many roads and streets have buried beneath them water lines, sanitary sewer lines and storm sewers. In order to permit access to these lines or pipes for purposes of repair, maintenance or inspection, manhole structures are provided at suitable locations along the road or street and these provide a vertical passageway by which one or more persons can gain access from ground level to the line or pipe. A common form of manhole includes a concrete enclosure that extends upwardly to a cast iron support frame in which is mounted a removable manhole cover, which cover is often circular. Ideally, the support frame and the manhole cover are mounted in such a way that the upper surface formed thereby is flush with the adjacent surface of the road or street. However, for reasons explained further hereinafter, it is quite common for the top of a manhole to sink or move out of alignment with the road surface with the passage of time, resulting in the formation of a cavity or hole in the road. Such holes can cause bumps for vehicular traffic and this can sometimes result in a dangerous situation.
Catch basins can be used in a variety of situations to gather ground water but perhaps most commonly they are used along the edge of paved streets or roadways, particularly ones that have some form of curb along one or both edges of the roadway. A common form of catch basin includes a concrete enclosure capable of holding water and having an open top covered with an iron grating which permits water to flow into the catch basin. Generally, the catch basin is connected by suitable piping to a nearby storm sewer line. Catch basins can be subject to the same problems as manholes, particularly if they are subjected to heavy vehicular traffic or the weight of large vehicles or trucks. Thus, the top of the catch basin can sometimes sink below the adjacent surface of the road or street.
One reason for the sinking of manhole tops is the use of rigid, annular concrete rings to adjust the height of the iron support frame at the top of the manhole. The constant and repetitive pounding of these adjustment rings by vehicles driving over the top of the manhole can eventually result in one or more of these rings being partially crushed or failing completely, thus allowing the top of the manhole to sink relative to the road surface. It is also possible for the top of the main manhole structure to wear away or fail with the passage of time, again permitting the top of the manhole sink.
Other difficulties can occur with known manhole and catch basin structures even when the top of the manhole or catch basin does non sink. For example, it can be difficult obtain optimum compaction of asphalt material adjacent the periphery of a manhole or catch basin and this can lead fairly rapid deterioration of the asphalt or other road surface adjacent to the manhole or catch basin. Furthermore, severe weather conditions or severe temperature changes can lead to expansion and contraction of the pavement, eventually leading to its breakup or cracking around the rigid structure formed by the manhole or catch basin. It should also be noted that once a bump develops at or around a manhole or catch basin, either the sinking of the manhole or catch basin or the deterioration of the adjoining flexible pavement surface can accelerate. This is because the existing bump will cause a rolling vehicle tire to generate an impact force which becomes greater with the size of the bump.
Recent U.S. Pat. No. 5,281,046 issued Jan. 25, 1994 to Domal Envirotech Inc. describes the use of a resilient, annular transition collar that can be placed around the top of a rigid roadway structure such as a manhole or catch basin. This collar acts as a flexible transition between the rigid frame of the structure and the semi-rigid or flexible asphalt paving. Adjustment rings can be provided below the collar in order to adjust its depth relative to the pavement surface and provide a flush fit. One perceived difficulty with this known transition collar however is that the joint between the outer peripheral wall of the collar and the adjoining pavement can deteriorate relatively quickly. One reason for this is that the movement of the resilient collar as vehicles pass over it tends to "pump" the adjacent granular material out of the space between the collar and the pavement. As this material is pumped out, water can seep into the space around the collar and the manhole. This water, particularly if it freezes in cold weather conditions, can eventually result in failure of either the top of the manhole structure or the adjoining pavement. In addition, such collars may work themselves partially out of the ground, thereby forming a potential road hazard.
U.S. Pat. No. 5,044,818 issued Sep. 3, 1991 to P. C. Pritchard describes a vertically adjustable manhole cover assembly. This assembly utilizes annular adjustment rings at both the top and bottom of a vertically adjusted annular sleeve positioned within the annular frame of the manhole cover supporting frame. The upper annular support ring includes an annular flange extending radially outwardly which is captured by the roadway resurfacing material so as to provide additional support to the cover assembly.
Also, recent U.S. Pat. No. 5,030,030 issued Jul. 9, 1991 Riedel Omni Products, Inc. describes a pad for supporting a utility access conduit in a roadway. The pad comprises a rectangular block of rubber or similar resilient elastomeric material which has an opening passing through it that snugly engages the access conduit. Shredded waste rubber from tires can be used to make the pad.